The impact of turbulence on star formation and supermassive black hole growth at high redshift

高红移条件下湍流对恒星形成和超大质量黑洞生长的影响

• 批准号: 1803466
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2016
• 资助国家: 英国
• 起止时间: 2016 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-1803466
• 关键词: impact; turbulence; star; formation; supermassive

Physical processes that play a key role in driving galaxy formation and evolution, such as star formation and stellar feedback, and super massive black hole formation, accretion and feedback, take place on extremely small, sub-galactic scales. For this reason, it is a tremendous challenge for numerical hydrodynamics simulations to capture both the environment of galaxies and meaningfully resolve their internal structure to identify the sites where stars form. In particular, the role played by compressible turbulence in shaping galaxy properties has received relatively little attention, even though it has long been known (Larson, 1981) that the cradles of star formation, i.e. molecular clouds, are supersonically turbulent. The aim of the project is therefore to try to bridge this gap and identify the relevant physical processes which drive turbulence in galaxies whilst also quantifying how this turbulence shapes the interstellar medium of galaxies and influences star/black hole formation. More specifically, this involves running/analysing high-resolution zoom (min 10pc) simulations of individual galaxies in their explicit cosmological context, to address the complex issue of the role played by the environment (large scale gas flows, fly-by encounters, mergers) in driving/triggering turbulence, and explicitly use the partially resolved turbulent cascade of the flow, measured on-the-fly in the simulations, to determine both the loci of star (black hole) formation and the efficiency of the star formation process. These simulations will then be compared to their "twins", i.e. simulations that are identical in every other aspect, except that star formation is determined by the current "standard" sub-grid modelling, i.e. a simple density threshold and a fixed, universal efficiency, empirically calibrated on the observed Kennicutt-Schmidt law (Kennicutt, 1998). Ultimately, the success of the turbulent star formation model will be judged by its capacity to recover the Kennicutt-Schmidt law (which, contrary to the standard model, is not built-in) while at the same time producing galaxies with dark matter to stellar mass ratios in agreement with observed values (Moster et al 2012, Behroozi et al 2013).

在驱动星系形成和演化中起关键作用的物理过程，如星星形成和恒星反馈，以及超大质量黑洞的形成，吸积和反馈，都发生在非常小的亚星系尺度上。因此，数值流体动力学模拟既要捕捉星系的环境，又要有意义地解析其内部结构，以确定恒星形成的位置，这是一个巨大的挑战。特别是，可压缩湍流在塑造星系性质中所起的作用，得到的关注相对较少，尽管人们早就知道（Larson，1981）星星形成的摇篮，即分子云，是超音速湍流。因此，该项目的目的是试图弥合这一差距，并确定驱动星系湍流的相关物理过程，同时量化这种湍流如何塑造星系的星际介质并影响星星/黑洞的形成。更具体地说，这涉及运行/分析高分辨率缩放（min 10 pc）在明确的宇宙学背景下模拟单个星系，以解决环境所起作用的复杂问题。（大规模气流，飞越相遇，合并）在驱动/触发湍流，并明确使用部分解决的湍流级联的流动，在模拟中测量的飞行，以确定星星（黑洞）形成的轨迹和星星形成过程的效率。然后将这些模拟与它们的“孪生”模拟进行比较，即在其他方面完全相同的模拟，除了星星的形成是由目前的“标准”子网格模型确定的，即一个简单的密度阈值和一个固定的通用效率，根据观察到的肯尼库特-施密特定律（肯尼库特，1998年）进行经验校准。最终，湍流星星形成模型的成功将通过其恢复肯尼库特-施密特定律（与标准模型相反，该定律不是内置的）的能力来判断，同时产生暗物质与恒星质量比与观测值一致的星系（Moster et al 2012，Behroozi et al 2013）。